def test_pop(self):
new_obj = object()
ordered_set = OrderedSet(['key', 1, '123', new_obj])
ordered_set.pop()
self.assertEqual(len(ordered_set), 3)
ordered_set.pop()
self.assertEqual(len(ordered_set), 2)
ordered_set.pop()
self.assertEqual(len(ordered_set), 1)
ordered_set.pop()
self.assertEqual(len(ordered_set), 0)
with self.assertRaises(KeyError):
ordered_set.pop()
